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mmap: add clarifying comment to vma_merge() code

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When tracing through the code in vma_merge(), it was not completely
clear why the error return to a dup_anon_vma() call would not overwrite
a previous attempt to the same function.  This commit adds a comment
specifying why it is safe.

Link: https://lkml.kernel.org/r/20230929183041.2835469-4-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Suggested-by: Jann Horn <jannh@google.com>
Link: https://lore.kernel.org/linux-mm/CAG48ez3iDwFPR=Ed1BfrNuyUJPMK_=StjxhUsCkL6po1s7bONg@mail.gmail.com/
Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Liam R. Howlett 2023-09-29 14:30:41 -04:00 committed by Andrew Morton
parent 651acf0ceb
commit 9a12d103f7
1 changed files with 5 additions and 0 deletions
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5
mm/mmap.c
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@ -943,6 +943,11 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
vma_start_write(curr);
remove = curr;
remove2 = next;
/*
* Note that the dup_anon_vma below cannot overwrite err
* since the first caller would do nothing unless next
* has an anon_vma.
*/
if (!next->anon_vma)
err = dup_anon_vma(prev, curr, &anon_dup);
}